91 
63 

y 1 



QUESTION SUMMARY 



TO ACCOMPANY 

"SOIL FERTILITY^AND PERMANENT 
AGRICULTURE" 



BY 



CYRIL G. HOPKINS, Ph.D. 

PROFESSOR OF AGRONOMY IN THE UNIVERSITY OF ILLINOIS 
CHIEF IN AGRONOMY AND CHEMISTRY AND VICE 
DIRECTOR OF THE ILLINOIS AGRICUL- 
TURAL EXPERIMENT STATION 



GINN AND COMPANY 

BOSTON • NEW YORK • CHICAGO • LONDON 
COPYRIGHT, 1912, BY GINN AND COMPANY 



QUESTION SUMMARY 

TO ACCOMPANY 

"SOIL FERTILITY AND PERMANENT 
AGRICULTURE" 



BY 



CYRIL G. HOPKINS, Ph.D. 

PROFESSOR OF AGRONOMY IN THE UNIVERSITY OF ILLINOIS 
CHIEF IN AGRONOMY AND CHEMISTRY AND VICE 
DIRECTOR OF THE ILLINOIS AGRICUL- 
TURAL EXPERIMENT STATION 



GINN AND COMPANY 

BOSTON . NEW YORK • CHICAGO • LONDON 
COPYRIGHT, 1912, BY GINN AND COMPANY 



d 



,0 



€GI.A31233i 



PREFATORY NOTE 

While the author recognizes that there is at least as much of 
mental culture in a study of plant-food compounds and of the 
bacteria of clover roots as there is in a study of Latin com- 
pounds and Greek roots, he also realizes that a course in soil 
fertility should do more than develop the mind. If there is any 
place for the " educated " man who is graduated with largely 
increased mental power but with litde positive addition to his 
own knowledge of facts and principles, that place is not in agri- 
culture. The educated farmer should have ready for his own use 
and defense some actual data supporting and establishing the 
most fundamental facts and principles upon which permanent 
agriculture must be based. It is worth many times the effort, 
for example, to memorize some half-century averages given to 
us by those noble men, Lawes and Gilbert, of Rothamsted. 

The following list of questions should help the student to 
understand what is important to know, and how to study with 
effectiveness and with economy of time and mental energy. The 
teacher may direct the class to check off certain questions which 
he feels are of too little importance or too difficult for the par- 
ticular class or for the time that can be devoted to this course of 
study ; and it is expected, of course, that additional questions 
will be asked, especially such as have large local interest which 
may be discussed in lectures embodying material supplementary 
to that contained in the text. (The local State Experiment 
Station bulletins should be of much value in this connection.) 
Many of the questions may be assigned as subjects for written 
articles, for the preparation of which the student should be 

812.3 iii 



iv QUESTION SUMMARY 

allowed a week or more, and often required to do some supple- 
mentary reading; but the most important and most carefully 
written paper required of the student should be in the nature 
of a definite plan and rather complete specifications or directions 
for the future management of his own farm in a system of truly 
permanent agriculture. The analysis of soil, made by himself 
if possible (in an accompanying laboratory course in soil fertility), 
should serve as a substantial basis for intelligent thinking, and 
it is highly desirable that he base his final plans upon such 
crop yields as he feels he has reason to assume can and will be 
produced. 

While some may plan to operate a grain farm and others a 
live-stock farm, the average student will probably plan a system 
of mixed husbandry, selling the more valuable grains, and pos- 
sibly hay too, when worth as much or more than grain, pound 
for pound (as with corn at 50 cents a bushel and hay at $18 
per ton), feeding the less valuable grain and forage, and saving 
labor by allowing live stock to gather the pasture crops and to 
return the resulting manures directly to the land. Aside from 
computing the amounts of fertility removed and returned to the 
soil, he should state the forms of plant food to be purchased, 
the rotation of crops, the substitute crops to be used in case of 
any crop failure, the rations to be fed (based upon his animal- 
husbandry- courses), the farm equipment, and probable labor 
required. Finally, he should assume reasonable prices and costs, 
and make as safe an estimate as possible upon the financial 
outcome. 

In the author's experience this is the most interesting and 
valuable work performed by his students, for it enables them 
to make definite plans to fit the principles of science into a 
knowledge of the actual practice of agriculture on a farm which 
is different, perhaps, in some respects, from any other farm. 

CYRIL G. HOPKINS 

University of Illinois 



QUESTION SUMMARY 

"SOIL FERTILITY AND PERMANENT 
AGRICULTURE" 



CHAPTER I 

1. Define science, element, atom, atomic weight, symbol. 

2. Define valence, compound, molecule, formula, chemical 
action. 

3. State the law of constant proportions. 

4. Discuss briefly the number and relative abundance of 
known elements. 

CHAPTER n 

5. Name fourteen common elements and give the symbol, 
atomic weight, and valence of each. 

6. Name the eight abundant elements in the earth's crust 
and state the approximate percentage of each. (47, 28, 8, 4^, 
3^, and three 2^.) 

7. Give the exact percentages of potassium, phosphorus, and 
sulfur reported for the earth's crust. 

8. Name five important elements in the ocean and give the 
percentages of potassium and of sodium chlorid. 

9. Name the four elements of the air and state the per- 
centage of each. 

10. Name the elements known to be essential for plant 
growth and give percentages of the three that are most abun- 
dant in corn. 



2 QUESTION SUMMARY 

11. Name six acid-forming elements and six base-forming 
elements ; give formulas for common acids and alkalis, and 
equations representing the formation of six salts containing 
these twelve elements. 

12. What element is contained in all acids ? 

13. Explain and illustrate acid salts, and monobasic, dibasic, 
and tribasic acids. 

CHAPTER III 

14. Discuss photosynthesis and condensation in the forma- 
tion of sugars, starch, and fiber. 

15. Explain the carbon-oxygen cycle. 

16. Give names and formulas for five fatty acids and two fats. 

17. Discuss the relative abundance of atmospheric carbon 
and nitrogen for plant growth. 

18. Give chemical names, formulas, and natural occurrence 
of oxalic acid, asparagin, and two intermediate products. 

19. Give names and occurrence of two proteids and discuss 
their composition and possible way of formation. 

20. Give formula and occurrence of allyl sulfid. 

21. Discuss occurrence and composition of nuclein. 

22. Name the elements known to exist as part of the plant 
structure or living tissue, and discuss the possible uses of the 
other elements essential for plant growth. 

23. Explain possible common functions of elements. 

24. Explain and illustrate the difference between requirement 
and toleration of elements by plants. 

CHAPTER IV 

25. Name the controlling element in organic compounds and 
the corresponding element in the abundant mineral compounds. 

26. Name two common rocks of the earth's crust and dis- 
cuss their formation. 

27. Name four important rock minerals and discuss their 
composition. 



SOIL FERTILITY 3 

28. Give names and formulas of three silicon compounds of 
natural occurrence. 

29. Discuss composition and properties of zeolites, sand, 
clay, and quartz. 

30. Discuss carbonates and give formulas of calcite, mag- 
nesite (MgCOg), and dolomite. 

31. Discuss losses of rock constituents by weathering and 
leaching. 

32. Give names and formulas of compounds of phosphorus 
and sulfur found in extensive natural deposits. 

CHAPTER V 

33. Define loess, glacial drift, alluvial soil, residual soil, and 
cumulose soil (see also page 75). 

CHAPTER VI 

34. Discuss the operation of natural laws with respect to soil 
enrichment and depletion on level uplands in humid climates. 

35. Explain the benefits of soil erosion. 

36. State the number of pounds of nitrogen, phosphorus, and 
potassium required (i) for the grain, and (2) for the straw or 
stover, for a 50-bushel crop of wheat, for loo-bushel crops of 
com and oats, and for 4 bushels of seed and 4 tons of clover ; 
also the magnesium and calcium required for the 4 tons of clover, 
and the total for the four crops of each of seven elements (see 
also pages 75 and 154). 

37. State the potassium content of the common prairie soil 
(surface) of the lower Illinoisan, middle Illinoisan, early Wisconsin, 
and late Wisconsin glaciations, and of west-central Minnesota; 
and give reason for differences. 

38. Discuss the nitrogen content of the common upland soils 
of the southern, northern, and western states, and give reasons 
for regional differences. 



4 QUESTION SUMMARY 

39. Explain the presence of carbonates and of acidity with 
reference to climate and to age of soil. 

40. State the phosphorus content of the black cotton soil of 
India, black earth soil of Russia (Von Ugrimov's report), of soil 
from Turkey in Asia (Massachusetts report), of Bavarian barrens, 
of Holland alluvium, of Blue-Grass surface soil and lower subsoil 
at the Kentucky Experiment Station, of New Mexican adobe 
soil, of Red River Valley soil, and of Illinois deep loess subsoil. 

41. State the number of pounds of nitrogen, phosphorus, and 
potassium in 2 million pounds of surface soil at Rothamsted, 
England, at State College, Pennsylvania, at Wooster, Ohio, at 
Urbana, Illinois, and at Columbia, Missouri. 

42. Give approximately the average composition of the princi- 
pal type of soil in each of five great soil areas in this state. 
(The teacher should furnish data in lectures to supplement the 
text where necessary and locally possible.) 

43. State approximately the average composition of Florida 
sand, of Wisconsin residual sand, of Illinois glacial sand, of 
Illinois black clay loam (early Wisconsin glaciation), and of 
deep peat soil (see also page 498). 

CHAPTER VII 

44. Describe Kossowitsch's experiment to ascertain if the 
presence of living plant roots influences the availability of 
plant food. 

CHAPTER VIII 

45. Name and locate (by map drawing) the fourteen soil 
provinces of the United States. 

CHAPTER IX 

46. Describe the location, topography, history, composition, 
productive power, and agricultural value of the '' Leonard town 
loam " and the " Marshall black clay loam." 



SOIL FERTILITY 5 

47. The total phosphorus and calcium in 2 million pounds 
of the surface soil of the '' Leonard town loam " would provide 
for how many 4-ton crops of clover ? 

48. Describe King's investigation to ascertain the plant food 
made available in poor and good soils. 



CHAPTER X 

49. State the number of pounds of nitrogen and phosphorus 
in 100 bushels of ear corn, in 2 bales of cotton lint, in 1000 
pounds of fat cattle, in 10,000 pounds of milk, in 500 pounds 
of butter. 

CHAPTER XI 

50. State the number of pounds of nitrogen, phosphorus, and 
potassium in i ton of average fresh manure, of average barn- 
yard manure, of corn stover, of oat straw, and of wheat straw. 

51. State the amount of nitrogen per ton in each of three 
nitrogen fertilizers, giving name of each. 

52. Name three bone fertilizers and state the average amount 
of nitrogen and phosphorus per ton of each. 

53. Give the amount and average market value of the phos- 
phorus in a ton of steamed bone meal, raw rock phosphate, acid 
phosphate, double superphosphate, and basic slag phosphate. 

54. Name three potassium salts used as fertilizers and state 
the number of pounds of potassium per ton of each. 

55. State the amounts of three important constituents in a 
ton of average wood ashes. 

56. How many pounds of nitrogen, '' available " phosphorus, 
insoluble phosphorus, and of potassium are contained in a ton 
of average '' complete " fertilizer ? 

57. What yield of corn is provided for by 200 pounds per 
acre of average "complete" fertilizer: (i) with respect to 
nitrogen ? (2) phosphorus ? (3) potassium ? 



6 QUESTION SUMMARY 

CHAPTER XII 

58. Name the three materials that must be applied to normal 
soils to provide systems of permanent agriculture (see page 159). 

59. In maintaining fertility without the purchase of potassium, 
how many years might be allowed for the removal by erosion of 
I inch of common corn-belt prairie soil from which one third 
of its potassium had been removed by cropping and leaching, 
if 50 bushels of wheat per acre were sold annually from the 
farm ? (See also page 561.) 

60. In power to correct soil acidity i ton of common lime- 
stone is equivalent to how many pounds of quicklime, of hydrated 
lime, of dolomitic limestone, of thoroughly air-slacked lime, purity 
being assumed ? 

61. Describe the Pennsylvania experiments with caustic lime 
and ground limestone, and give figures to show their comparative 
effect upon crop yields, soil nitrogen, and organic matter. 

62. Describe the Maryland experiments with carbonate and 
caustic lime. 

63. At what rate and frequency should limestone be applied 
per acre in humid sections in order to insure its maintenance } 
(See also page 561.) 

64. Give a reason for testing the subsoil for acidity and 
evidence indicating that soil acidity is due in part to inorganic 
acid salts. 

65. Why should limestone and phosphate not be applied in 
intimate contact ? 

66. Discuss the degree of fineness desirable for limestone to 
be used in soil improvement in humid sections. 

CHAPTER XIII 

67. Name the three great natural sources of phosphorus. 

68. As an average what proportion of the phosphorus re- 
quired for grain crops is retained in the straw and stover, 



SOIL FERTILITY y 

and what proportion is possibly recoverable in the manures in 
average live-stock farming ? 

69. Explain the manufacture of acid phosphate and double 
superphosphate. Show reactions and state the percentage of 
phosphorus in each, if made from pure materials. 

CHAPTER XIV 

70. Discuss active and inactive organic matter and define 
humus. 

71. Explain ammonification and nitrification, and name three 
important requirements in the process. 

72. Name three decomposition products of organic matter 
which may aid in liberating plant food from insoluble minerals, 
and express a quantitative comparison with respect to nitrogen 
and phosphorus. 

7 3 . Name three practical methods of supplying organic matter. 

74. Describe the experiments in Maryland and Canada on 
losses of organic matter by exposing manure. 

75. As an average what proportion of the organic matter and 
nitrogen in feed is possibly recoverable in the manure in live- 
stock farming ? 

76. Describe the Cambridge experiments with losses of plant 
food from manure and from oil-cake fed. 

77. Explain parasitism, symbiosis, nitrogen fixation. 

78. Discuss the relative abundance, in existing suitable form, 
of oxygen and nitrogen for the production of legume plants 
properly infected. 

79. Explain the need and most practical method of inoculation. 

80. On soils of moderate productivity, about what proportion 
of the nitrogen for well-infected legume plants is secured from 
the soil 1 Give basis for opinion. 

81. About what proportion of the total nitrogen in the plant 
is contained in the roots and stubble of red clover ? of cowpeas ? 



8: QUESTION SUMMARY 

82. Discuss the Illinois investigation with sweet clover, and 
express its manurial value per acre in terms of farm manure. 

83. Discuss nitrogen fixation by nonsymbiotic bacteria. 

CHAPTER XV 

84. Plan a practical system of grain farming which shall main- 
tain soil fertility without the purchase of nitrogen in any form, 
giving figures (on assumed yields) for organic matter and fertility 
elements removed and supplied per acre for one rotation period. 

CHAPTER XVI 

85. Plan a practical system of live-stock farming which shall 
maintain the fertility of the soil without the purchase of nitrogen 
in any form, giving figures (on assumed yields) for organic matter 
and fertility elements removed and supplied per acre for one 
rotation period. 

CHAPTER XVII 

86. Name four neutral insoluble phosphorus fertilizers of 
animal origin, seven insoluble mineral phosphates, one insoluble 
alkaline phosphate, and four soluble phosphorus fertilizers of 
acid reaction. 

87. Discuss the use of phosphatic marl as a source of phos- 
phorus for crops. 

88. Name three important points to be kept in mind 
when trying to determine fertilizer requirements from culture 
experiments. 

89. Describe the Ohio manure-phosphate experiments, giving 
exact figures to show comparative returns from raw phosphate 
and acid phosphate. 

90. Describe the Maryland experiments with different forms 
of phosphorus, giving some specific information as to results. 

91. Describe the Pennsylvania experiments with different 
forms of phosphorus, and give some specific data as to results. 



SOIL FERTILITY 9 

92. Give some definite information as to the results of the 
Rhode Island experiments with different phosphates. 

93. Summarize the results of the Maine and Massachusetts 
experiments with different phosphates. 

94. Discuss the Indiana and Illinois experiments with 
phosphorus. 

95. Discuss briefly the report of the National Fertilizer 
Association on " Raw Rock Phosphate." 

CHAPTER XVIII 

96. Describe Van Helmont's experiment and state Bradley's 
opinion concerning the food of plants. 

97. Discuss Jethro Tull's plant-food theories, and also state 
the views of Thaer and Hunter. 

98. Name the discoveries of Priestly, S^nebier, and De 
Saussure. 

99. Name the important truth established by Lawes and 
Gilbert, and the late discovery by Hellriegel, relating to 
nitrogen. 

100. Discuss Liebig's views as to the principal source of 
nitrogen for plants; also state how many pounds of nitrogen 
are contained in normal rainfall per acre per annum. 

101. Describe Decandolle's theory as to the need and value 
or reason for crop rotation. 

102. Describe and discuss briefly the soil-fertility theories of 
Whitney and Cameron, especially with reference to the law of 
solution, the rise of plant food from the lower subsoil, and the 
effect of manures and fertilizers on crop yields (see also 
page 366). 

103. Give some facts and figures concerning the early and 
continued use of phosphorus in European countries, and estimate 
the amount of phosphorus applied in 20 loads of bones of 40 
bushels each (see also page 636). 



lO QUESTION SUMMARY 

104. Give some reasons for changes in crop yields in western 
Europe during the last century. 

105. Contrast the agricultural conditions and practices of the 
Aryan race in Russia and India with those of the Mongolian 
race in China and Japan (see also page 594). 

CHAPTER XIX 

106. Discuss the origin and conduct of the Rothamsted 
Experiment Station, name the principal field experiments, and 
state the duration of each. 

107. Give some definite figures from Agdell field showing the 
effect on crop yields of long-continued cropping without fertilizing. 

108. At prices given on page 359, state exactly the cost and 
value of the increase produced per acre by phosphorus in 36 
years in the legume system with the turnips fed on Agdell field. 
(Problem to be assigned in advance and answer memorized. 
See notes on pages 346, 354.) 

109. Give the treatment and average yields on plots 2,3, and 
8 on Broadbalk field. 

110. Discuss the effect of successive increments of nitrogen 
on the yield of wheat on Broadbalk field. 

111. Give in round numbers the average annual rainfall at 
Rothamsted, and in northern and southern Illinois, in Tennessee, 
and in this state. (Teacher to supply data in class.) 

112. Give the treatment and average yields of barley for 
three plots on Hoos field (e.g. O i, A 4, N 2). 

113. Compare the durability in the soil of farm manure, 
soluble nitrogen, and minerals applied. 

114. Give the treatment and average yields of potatoes for 
four plots on Hoos (e.g. i, 2, 8, 9). 

115. Discuss the use of acid phosphate as a top-dressing for 
permanent grass lands. 

116. Give the treatment and approximate average yields of 
hay for five plots on The Park at Rothamsted (e.g. 3, 5, 7, 9, n)- 



SOIL FERTILITY II 

117. Compare the effect of salts containing potassium with 
that of other alkali salts on the yield of wheat, barley, and hay 
at Rothamsted. (Memorize differences between average yields 
of plots 12 and 13 on Broadbalk, A 4 and N 2 on Hoos, and 
note 4-2, 10, and 9 on The Park.) 

118. Discuss the apparent influence of potassium on the bo- 
tanical composition of the herbage on The Park, and the resulting 
effect on total yield. (Compare plots 7 and 8 with 9 and 10.) 

119. In what different ways may alkali salts bring about 
increases in crop yields ? (Note the effect of phosphorus on 
Agdell clover in 1874 and 1882 and compare with results from 
plots 3 and 12, 4-1 and 7 on The Park.) 

120. Discuss the effect of enriching the surface upon the 
plant food removed from the subsurface and subsoil. (Com- 
pare plots 3, 4, and 5 with 7, 12, 13, and 14, page 411.) 

121. Discuss the relation between the yields of crops and 
their content of phosphorus and of potassium. (Compare plots 
4-1 and 7, plots 4-2 and 9, etc., page 418.) 

CHAPTER XX 

122. Describe the Pennsylvania field experiments with ferti- 
lizers, and state briefly the effect of nitrogen, phosphorus, and 
potassium, singly and combined. 

123. Give figures from the Pennsylvania experiments to show 
the effect upon productivity of crop rotation without fertilization. 

124. Explain why it is practically impossible to completely 
exhaust the fertility of any soil. 

125. Explain how apparent increase from long-continued soil 
treatment in comparison with no treatment may really represent 
no increase in productivity. 

126. Discuss the variation due to soils and crops in the agri- 
cultural value of a ton of manure. 

127. Discuss the Pennsylvania experiments with reference 
to the maintenance of soil nitrogen. 



12 QUESTION SUMMARY 

128. In permanent agriculture should the apparent increase 
from the return of plant food needed to maintain initial produc- 
tivity have any place in the computed profits ? 

CHAPTER XXI 

129. Discuss (i) the common effects of a good rotation in 
comparison with no rotation or with a poor rotation previously 
practiced ; and (2) the probable relation of crop yields during the 
second or third rotation period in comparison with the first and 
with the subsequent periods. 

130. Describe the Ohio experiments with various fertilizers 
at Wooster and Strongsville. 

131. Summarize the results of the Ohio experiments with 
special reference to the need and effect of nitrogen, phosphorus, 
and potassium. 

132. State the return per dollar invested in phosphorus when 
applied in addition to nitrogen and potassium in the five-year 
rotation at Wooster and Strongsville, and suggest a practical 
method of utilizing this knowledge. (Problem to be assigned in 
advance and answers memorized.) 

133. State the essential facts secured in the Ohio experi- 
ments with bone meals in comparison with factory-mixed " com- 
plete " fertilizers. 

CHAPTER XXII - 

134. Four-ton crops of clover (or 90-bushel crops of corn) 
per acre each year since Columbus discovered America would 
have required the total phosphorus to about what depth in the 
common Illinois corn-belt prairie soil ? 

135. Describe the Illinois field experiments at Urbana, and 
give some definite figures showing the effect of rotation and of 
soil treatment upon the yield of corn. 

136. What important facts are emphasized by the results from 
the Illinois experiments at Sibley ? 



SOIL FERTILITY 13 

137. Summarize the ten years' results from the Illinois experi- 
ments at Bloomington. 

138. Compare rock phosphate and feldspar or granite with 
reference to their use in soil enrichment. 

139. Describe the Illinois experiments on sand soil at Green 
Valley, giving some figures to show the most important results. 

140. Describe the Illinois experiments on peaty swamp land 
at Manito, and discuss the effects of limestone, phosphorus, 
potassium, sodium, land-plaster, and manure. 

141. Discuss peaty alkali soils. (Alkali soils in humid sections 
are formed by the evaporation from exposed land surface of 
drainage or seepage waters, as from old swamps or along 
their borders.) 

CHAPTER XXIII 

142. Give figures showing the effect of green manure, lime- 
stone, and phosphorus on wheat on the Illinois experiment field 
at Odin. 

143. Give data from the Illinois experiments at Eairfield 
bearing upon the use of potassium. 

144. If 50 bushels of wheat per acre were sold annually from 
the common prairie land of southern Illinois, how many years 
would be required to thus take from the farm as much potassium 
as is contained in 2 million pounds of the surface soil ? 

145. Suggest practical treatment for the loess-covered hill 
lands of the South Central states, citing results of experiments to 
support the suggestions. 

146. Why is the application of phosphorus usually less impor- 
tant on sloping uplands than on those of more nearly level 
topography ? 

147. Compare the general results of field experiments reported 
from southern Iowa and from northern Mississippi. 

148. What general conclusions are indicated by the Georgia 
and Alabama experiments with fertilizers for corn and cotton ? 



14 QUESTION SUMMARY 

149. Describe the Louisiana experiments at Calhoun and 
give figures summarizing the average results secured. 

150. Compare the values per acre of corn and cotton and 
the draft upon the stock of fertility when corn and cotton lint 
are sold. 

CHAPTER XXIV 

151. Discuss the Minnesota experiments with reference to 
the maintenance of nitrogen. 

CHAPTER XXV 

152. Describe and summarize the Canadian field experiments, 
especially with reference to fresh and rotted manure and differ- 
ent forms of phosphorus. 

CHAPTER XXVI 

153. Discuss the value of the short-time culture methods of 
Whitney and Cameron in comparison with long-continued field 
experiments for determining fertilizer requirements. 

CHAPTER XXVII 

154. Give the average composition and discuss the cost and 
use of common " complete " commercial fertilizers. 

155. What percentage increase in crop yield might reasonably 
be expected from the nitrogen and " humus effect " of 50 pounds 
of dried peat soil applied as a filler in 200 pounds of " com- 
plete " fertilizer (i) on the brown silt loam of the corn belt, and 
(2) on the soil at Wooster, Ohio ? (In humus the ratio of nitro- 
gen to carbon approaches i to 10, and the ratio of carbon to 
organic matter is nearly i to 2.) 

156. Name four forms of commercial nitrogen and give 
examples and pounds of nitrogen per ton of each. 

157. Describe two commercial processes for the artificial 
fixation of atmospheric nitrogen. 



SOIL FERTILITY 1 5 

158. Name three different sources of commercial potassium 
and three commercial products from the present most important 
source, giving pounds of potassium per ton of each. 

CHAPTER XXVIII 

159. Discuss crop stimulants and protective agents, giving 
illustrations. 

CHAPTER XXIX 

160. Mention some critical periods in plant life and explain 
the possibility of exaggerated effects from materials applied as 
plant food. 

CHAPTER XXX 

161. Name four factors governing the composition of manure. 

162. State the number of pounds of nitrogen, phosphorus, 
potassium, and organic matter in i ton (i) of average fresh 
stable manure, (2) of average rotted yard manure. 

163. How much manure containing 85 per cent of moisture 
is equivalent to 4 tons of the same kind of manure containing 
62^ per cent of moisture ? 

164. About how would it affect the composition of a ton of 
average fresh manure to replace the urine with rain water ? 

165. Name four factors influencing the agricultural value of 
average or '' standard " manure. 

166. Give data from field experiments showing some actual 
variations secured in the agricultural value of manure. 

167. Discuss the use of materials for preserving or increasing 
the value of manure, and cite some definite results secured. 

168. Give data showing losses from exposure of manure. 

CHAPTER XXXI 

169. Discuss briefly the removal of plant food from plants 
exposed to the weather. 



l6 QUESTION SUMMARY 

CHAPTER XXXII 

170. Name four ways in which plant food may be lost or 
removed from the soil. 

171. State about the average amounts of phosphorus, potas- 
sium, magnesium, and calcium lost per year in drainage water 
from an acre of normal land in humid sections. 

172. Discuss the Rothamsted investigations showing loss of 
nitrogen by leaching, and give method of prevention and data to 
prove its effectiveness. 

173. Discuss loss of nitrogen from soils as reported from the 
Minnesota and Canadian investigations. 

174. Explain how erosion may contribute toward the main- 
tenance of mineral plant food in the surface soil. 

175. Where the upland surface soils are poor in minerals and 
nitrogen compare the probable effects of gullying and sheet 
washing from the hills upon the fertility content of the over- 
flowed bottom land. 

176. Suggest methods for preventing the loss of plant food 
caused by erosion. 

CHAPTER XXXIII 

177. Explain the fixation of bases and phosphorus' in soils, 
giving possible reactions, and state how nitrate nitrogen may be 
fixed in the soil. 

CHAPTER XXXIV 

178. Describe practical qualitative tests for soil acidity and 
for limestone in the soil. 

179. Name suitable materials in which to supply nitrogen and 
phosphorus in fertilizer experiments; also name objectionable ma- 
terials for nitrogen, phosphorus, and potassium, and give reasons. 

180. If the soil is deficient in calcium or magnesium capable 
of ready liberatijon for plant food, in what form could they be 
economically applied ? 



SOIL FERTILITY 17 

CHAPTER XXXV 

181. What element or elements are likely to be deficient or 
abundant (i) in peat soils ? (2) in '' clay " soils ? (3) in residual 
sand soils ? (4) in glacial sand soils ? (5) in limestone soils ? 

CHAPTER XXXVI 

182. Name the six essential positive factors in crop produc- 
tion, and mention one example of possible improvement for 
each factor. 

183. Discuss briefly the rainfall records of North Platte, 
Nebraska, as representative of the semiarid region. (Late 
records show 22.41 inches for 1909, and 10.70 for 19 10, which 
is the lowest record in 36 years, a^veraging 18.63 inches, with 
19.14 for 1875-1892, and 18.12 for 1893-1910. By nine-year 
periods the averages are 19.95, ^^-33^ i4-54' ^^^ 21.70, with 
23.07 as the average for the eight years ending 1909, or almost 
60 per cent above the previous nine-year average.) 

184. Compare roughly (by map drawing) the humid and 
semiarid regions of the United States, receiving more and less, 
respectively, than 20 inches as the average annual rainfall. 

185. Compare the total area of farm land in the United States 
(873,729,000 acres. United States Census of 1910) with the 
area possible to be added by irrigation and drainage. (The 
United States Department of Agriculture estimates the total 
area of land capable of cultivation at 950,000,000 acres.) 

CHAPTER XXXVII 

186. If $2 per acre yearly invested in soil improvement would 
increase the crop yields by the equivalent of 2 bushels of corn 
per acre each year above the preceding year, what would be the 
cost per bushel for the increase in the fifteenth year ? 



I8 QUESTION SUMMARY 



CHAPTER XXXVIII 



187. If it costs $4 an acre to grow corn and 5 cents a bushel 
to harvest and market the crop, with interest at 5 per cent, taxes 
at .5 per cent, and corn at 40 cents a bushel, what is land 
apparently worth that will produce 20 bushels of corn per acre ? 
40 bushels? 80 bushels? 100 bushels? At what yield does the 
land become valueless ? What other necessary item of expense 
should be included to protect capital invested in land, and what 
are some of the results in the United States from neglecting 
this item ? 

CHAPTER XXXIX 

188. Summarize the history, rules, and ultimate results of the 
agricultural teaching and practice of the ancient Mediterranean 
countries (see also page 302). 



APPENDIX 



SECTION I 

189. Name four Western and three Eastern states in which 
extensive high-grade phosphate deposits are known to exist. 
(Montana is now in this list ; and some high-grade rock has 
been found near Midway, Kentucky, for which point some soil 
analyses are given on page 65. A United States Geological 
Survey press bulletin, released for publication on November i o, 
191 1, states that the work of the Geological Survey shows 
approximately 2^ billion long tons of phosphate averaging 
14 per cent phosphorus, corresponding to 70 per cent of tri- 
calcium phosphate, in the Western states. The bulletin adds : 
^' Nor does this include the tonnage of the Montana phosphate 
withdrawals, which aggregate nearly 34,000 acres.") 

190. Discuss the domestic supplies, consumption, and exporta- 
tion of natural phosphates. 

191. Discuss the source and consumption of phosphate in 
other countries. 

SECTION II 

192. Discuss the advantages and disadvantages of using the 
element system of nomenclature for reporting analyses of soils 
and fertilizers. 

SECTION III 

193. Compare the composition of unleached wood ashes and 
soft coal, also of wheat flour and wheat bran, as foods for 
growing animals (domestic or human). 

19 



20 QUESTION SUMMARY 

SECTION IV 

194. Compare the average estimated production, price, expor- 
tation, and apparent percentage increase in domestic consump- 
tion of corn and wheat for 1896- 1900 and 1906-19 10 with the 
percentage increase in population for the same decade. (See note, 
page 617. The Illinois corn acreage is reported for 1899 and 
1909, respectively, as 10,266,335 ^^^ iOj045337 by the 
United States Census; as 6,941,548 and 7,288,563 by the 
Illinois State Board of Agriculture; and as 6,865,287 and 
10,300,000 by the United States Department of Agriculture.) 

195. Give the increase or decrease in yield per acre by 
twenty-year averages (1866-1885 and 1886-1905) for corn 
and wheat in the United States ; also compare the total pro- 
duction of wheat in the Dakotas with that of all states east of the 
Mississippi (excepting Indiana and Illinois) for the year 1909. 

196. Compare the ten-year average yields of wheat of Russia, 
the United States, this State, Germany, United Kingdom, and 
Denmark, and give your opinion as to the causes for the 
greater yields in western Europe. 

197. Compare the phosphorus content of the phosphate ex- 
ports with that of the wheat produced in the United States. 

198. Compare the plant-food content of the wheat crop and 
of the butter exports of Denmark with that of the foodstuffs 
imported into that country. (Denmark imports about as much 
barley as corn, and about as much mill products as oil cake.) 

SECTION V 

199. Name the determinations that should be made in ana- 
lyzing a soil from the humid section, in order to secure definite 
information upon which to base plans for a practical system of 
permanent agriculture. 

200. What is the significance in soil analysis of dry matter, 
of organic carbon, of total calcium, of calcium carbonate equiva- 
lent to carbonate carbon, of calcium carbonate required ? 



APPENDIX 21 



SECTION VI 



201. Compare the average phosphorus content of the soils 
of the British Isles with that of the common corn-belt prairie 
land, and with that of the abandoned " Leonard town loam " of 
Maryland. 

202. How do you account for the great variation in phos- 
phorus content of English soils of the same soil type or forma- 
tion ? (See also pages 304 and 324.) 

203. Suggest some specific improvement which in your 
opinion might well be made either in the textbook or in the 
teaching of the subject. 



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SOIL FERTILITY 
LABORATORY MANUAL 

By Cyril George Hopkins, Professor of Agronomy in the University of Illinois, and 
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A GUIDE to laboratory work in soil fertility, including experiments 
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